This invention relate to the dehydrohalogenation of halogenated hydrocarbons. More specifically, it pertains to a process and a catalyst for the dehydrohalogenation of halogenated hydrocarbons to produce the corresponding unsaturated halohydrocarbon or unsaturated hydrocarbon.
Unsaturated halohydrocarbons and unsaturated hydrocarbons are extremely useful for the preparation of various polymeric compositions. For example, 1,1-dichloroethene, commonly known as vinylidene chloride, can be used to produce vinylidene chloride polymers. Vinylidene chloride polymers have an extremely high barrier resistance to the transmission of oxygen and water vapors. Thus, such polymers, particularly copolymers of vinylidene chloride and vinyl chloride, acrylates or other monomers, are very useful as films or coatings in food packaging composites. Other copolymers produced from vinylidene chloride show excellent resistance to solvents and corrosive chemicals and have a high degree of abrasion resistance, toughness and dimensional stability. Such durable copolymers are extremely useful in rigid extrusions, tank linings, monofilaments, and paint and cement additives.
U.S. Pat. No. 3,984,489 describes a process for preparing vinylidene chloride by the caustic dehydrochlorination of 1,1,2-trichloroethane in the presence of an amine. This caustic cracking of a chlorinated hydrocarbon leads to the formation of a salt stream which leads to waste deposit problems and causes the loss of chlorine.
U.S. Pat. Nos. 2,765,340; 2,803,678 and 2,803,679 describe a dehydrochlorination process utilizing a metal salt or metal oxide as a catalyst. U.S. Pat. No. 3,230,181 describes a dehydrohalogenation process utilizing calcium bromide as a catalyst. United Kingdom patent application No. 2,008,117A describes the preparation of vinylidene chloride by the vapor phase dehydrochorination of 1,1,2-trichloroethane in the presence of a cesium halide catalyst. U.S. Pat. Nos. 4,144,192 and 4,225,519 describe the dehydrochlorination of 1,1,2-trichloroethane in the presence of a cesium nitrate catalyst. U.S. Pat. No. 3,870,762 discloses a vapor phase dehydrochlorination process utilizing a chloride or fluoride of potassium, rubidium or cesium.
The above processes utilizing a catalyst suffer from deactivation of the catalyst due to the formation of coke on the catalyst surface. The formation of by-products and/or low selectivity to the desired products are also continuing problems in dehydrohalogenation reactions in general.
What is needed is an efficient dehydrohalogenation process that would avoid the waste disposal and halogen loss problems of prior methods by providing a means for safely and economically removing any salt or hydrogen halide produced by the dehydrohalogenation reaction. A process is also needed that would utilize a catalyst which would not rapidly deactivate due to coke deposition on the catalyst surface. A process is also needed that would provide for a high selectivity of the desired dehydrohalogenated product.